I would love the ability to add a second sitemap for W3TC Cache Preload. Here's why: I have many pages on my site that are produced by the dsidxpress plugin and are not part of the WP database. So these pages are not in my normal sitemap. I'd like to enter a second sitemap URL which would include those plugin-produced pages so W3TC can preload & cache them. Is there any way to do this? If not now, any chance a second sitemap option could be added in a future version?